Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 5 de 5
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Nature ; 500(7460): 98-101, 2013 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-23831649

RESUMO

Protein folding is often described as a search process, in which polypeptides explore different conformations to find their native structure. Molecular chaperones are known to improve folding yields by suppressing aggregation between polypeptides before this conformational search starts, as well as by rescuing misfolds after it ends. Although chaperones have long been speculated to also affect the conformational search itself--by reshaping the underlying folding landscape along the folding trajectory--direct experimental evidence has been scarce so far. In Escherichia coli, the general chaperone trigger factor (TF) could play such a role. TF has been shown to interact with nascent chains at the ribosome, with polypeptides released from the ribosome into the cytosol, and with fully folded proteins before their assembly into larger complexes. To investigate the effect of TF from E. coli on the conformational search of polypeptides to their native state, we investigated individual maltose binding protein (MBP) molecules using optical tweezers. Here we show that TF binds folded structures smaller than one domain, which are then stable for seconds and ultimately convert to the native state. Moreover, TF stimulates native folding in constructs of repeated MBP domains. The results indicate that TF promotes correct folding by protecting partially folded states from distant interactions that produce stable misfolded states. As TF interacts with most newly synthesized proteins in E. coli, we expect these findings to be of general importance in understanding protein folding pathways.


Assuntos
Proteínas de Escherichia coli/metabolismo , Proteínas Ligantes de Maltose/química , Proteínas Ligantes de Maltose/metabolismo , Chaperonas Moleculares/metabolismo , Peptidilprolil Isomerase/metabolismo , Dobramento de Proteína , Sítios de Ligação , Citosol/metabolismo , Escherichia coli/química , Escherichia coli/metabolismo , Proteínas Ligantes de Maltose/biossíntese , Modelos Moleculares , Pinças Ópticas , Peptídeos/química , Peptídeos/metabolismo , Biossíntese de Proteínas , Conformação Proteica , Redobramento de Proteína , Estabilidade Proteica , Estrutura Terciária de Proteína , Ribossomos/metabolismo , Espectroscopia de Infravermelho com Transformada de Fourier
2.
Mol Biosyst ; 6(4): 620-7, 2010 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-20237639

RESUMO

SecB is a molecular chaperone in Gram-negative bacteria dedicated to the post-translational translocation of proteins across the cytoplasmic membrane. The entire surface of this chaperone is used for both of its native functions in protein targeting and unfolding. Single molecule studies revealed how SecB affects the folding pathway of proteins and how it prevents the tertiary structure formation and aggregation to support protein translocation.


Assuntos
Proteínas de Bactérias/metabolismo , Chaperonas Moleculares/metabolismo , Transporte Proteico , Proteínas de Bactérias/química , Bactérias Gram-Negativas/metabolismo , Modelos Biológicos , Modelos Moleculares , Chaperonas Moleculares/química , Dobramento de Proteína , Processamento de Proteína Pós-Traducional , Biologia de Sistemas
3.
Biochemistry ; 49(11): 2380-8, 2010 Mar 23.
Artigo em Inglês | MEDLINE | ID: mdl-20146530

RESUMO

The molecular chaperone SecB binds to hydrophobic sections of unfolded secretory proteins and thereby prevents their premature folding prior to secretion by the translocase of Escherichia coli. Here, we have investigated the effect of the single-residue mutation of leucine 42 to arginine (L42R) centrally positioned in the polypeptide binding pocket of SecB on its chaperonin function. The mutant retains its tetrameric structure and SecA targeting function but is defective in its holdase activity. Isothermal titration calorimetry and single-molecule optical tweezer studies suggest that the SecB(L42R) mutant exhibits a reduced polypeptide binding affinity allowing for partial folding of the bound polypeptide chain rendering it translocation-incompetent.


Assuntos
Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Escherichia coli , Interações Hidrofóbicas e Hidrofílicas , Chaperonas Moleculares/química , Chaperonas Moleculares/metabolismo , Dobramento de Proteína , Adenosina Trifosfatases/química , Adenosina Trifosfatases/metabolismo , Substituição de Aminoácidos , Proteínas da Membrana Bacteriana Externa/metabolismo , Proteínas de Bactérias/genética , Proteínas de Escherichia coli/metabolismo , Proteínas Ligantes de Maltose , Proteínas de Membrana Transportadoras/química , Proteínas de Membrana Transportadoras/metabolismo , Modelos Moleculares , Chaperonas Moleculares/genética , Mutação , Peptídeos/metabolismo , Proteínas Periplásmicas de Ligação/metabolismo , Precursores de Proteínas/metabolismo , Estrutura Quaternária de Proteína , Transporte Proteico , Canais de Translocação SEC , Proteínas SecA
4.
Science ; 318(5855): 1458-61, 2007 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-18048690

RESUMO

How chaperone interactions affect protein folding pathways is a central problem in biology. With the use of optical tweezers and all-atom molecular dynamics simulations, we studied the effect of chaperone SecB on the folding and unfolding pathways of maltose binding protein (MBP) at the single-molecule level. In the absence of SecB, we find that the MBP polypeptide first collapses into a molten globulelike compacted state and then folds into a stable core structure onto which several alpha helices are finally wrapped. Interactions with SecB completely prevent stable tertiary contacts in the core structure but have no detectable effect on the folding of the external alpha helices. It appears that SecB only binds to the extended or molten globulelike structure and retains MBP in this latter state. Thus during MBP translocation, no energy is required to disrupt stable tertiary interactions.


Assuntos
Proteínas de Bactérias/metabolismo , Proteínas de Escherichia coli/química , Proteínas Periplásmicas de Ligação/química , Dobramento de Proteína , Simulação por Computador , Proteínas de Escherichia coli/metabolismo , Modelos Moleculares , Pinças Ópticas , Proteínas Periplásmicas de Ligação/metabolismo , Conformação Proteica , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína
5.
J Cell Biol ; 165(2): 213-22, 2004 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-15096523

RESUMO

The Escherichia coli YidC protein belongs to the Oxa1 family of membrane proteins that have been suggested to facilitate the insertion and assembly of membrane proteins either in cooperation with the Sec translocase or as a separate entity. Recently, we have shown that depletion of YidC causes a specific defect in the functional assembly of F1F0 ATP synthase and cytochrome o oxidase. We now demonstrate that the insertion of in vitro-synthesized F1F0 ATP synthase subunit c (F0c) into inner membrane vesicles requires YidC. Insertion is independent of the proton motive force, and proteoliposomes containing only YidC catalyze the membrane insertion of F0c in its native transmembrane topology whereupon it assembles into large oligomers. Co-reconstituted SecYEG has no significant effect on the insertion efficiency. Remarkably, signal recognition particle and its membrane-bound receptor FtsY are not required for the membrane insertion of F0c. In conclusion, a novel membrane protein insertion pathway in E. coli is described in which YidC plays an exclusive role.


Assuntos
Proteínas de Escherichia coli/metabolismo , Proteínas de Membrana/biossíntese , Proteínas de Membrana Transportadoras/metabolismo , ATPases Mitocondriais Próton-Translocadoras/metabolismo , Subunidades Proteicas/metabolismo , Adenosina Trifosfatases/metabolismo , Proteínas de Bactérias/metabolismo , Membrana Celular/química , Membrana Celular/metabolismo , Lipossomos/química , Lipossomos/metabolismo , Substâncias Macromoleculares , Potenciais da Membrana , ATPases Mitocondriais Próton-Translocadoras/química , Modelos Moleculares , Estrutura Secundária de Proteína , Prótons , Canais de Translocação SEC , Proteínas SecA , Partícula de Reconhecimento de Sinal/metabolismo , Vesículas Transportadoras/química , Vesículas Transportadoras/metabolismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...